“We do have a lot of arms down there now,” Collins said. “I’m intrigued to use [Isringhausen] in those big situations.”

He has to be, considering what else he and pitching coach Dan Warthen have down there.

Because while the Mets were searching for discounts among discarded relievers this offseason in an attempt to cobble together a bullpen capable of keeping them in contention, they also were relying on Parnell finally making the next step to being a reliable eighth-inning pitcher.

But like much of that plan, Parnell has not met expectations, including on Monday, when he gave up three runs and took the loss.

“If he keeps struggling in that role, we will go elsewhere,” Warthen said. “We’ll go with the hot hand, which might be [Isringhausen], Pedro Beato or D.J. Carrasco. We’re looking, but nobody is jumping out.”

That’s what happens when a pen has allowed 50 hits, 18 walks and a HBP in 38 innings this season. Overall, the pitching staff is ranked 27th in the majors at 5.30.

Warthen said part of the problem is not being able to find replacements for free-agent departures Hisanori Takahashi and Pedro Feliciano.

“We always had the reliability of those two out there,” said Warthen, who famously implied that the Mets knew Feliciano would encounter arm problems this season because of how much he was used in Flushing over the years.

“We felt all right that we could get through the seventh and eighth and hand it over to [Francisco Rodriguez]. It’s too early to tell how pronounced not having them is going to be.”

But Warthen’s primary concern is the eighth.

“That’s my biggest thing,” Warthen said. “Bobby is either going to step up and do the job or we’ll have to find someone else. Other than that, I think we’ll be fine.”

Parnell, just as he did a year ago when he couldn’t figure out how to succeed in that crucial role, is confident he will figure it out.

“I haven’t lost any confidence,” Parnell said.

Said Isringhausen, “Bobby is going to be fine. It doesn’t matter what inning. He’s got the stuff to do it, he’s got the heart. I’m here if he wants to talk to me about anything, but he’ll be OK.”

The Mets would like to believe Isringhausen is right.

“This guy has a great arm,” Collins said of Parnell. “He should go out there, and if he makes pitches with his good fastball, he’s going to get outs. One of the things he’s got to realize is, once in a while you’re going to get hit.”

He’s not alone in his struggles.

“We’re not happy with the performance,” Warthen said.

“It’s not like we’re getting killed, but we’re making too many silly mistakes like errors and not holding runners on, doing the stuff young staffs will do. But here, you can’t get away with it.”